131

Collapse of the Arctoscopus japonicus Catch in the Sea of Japan－Environmental Factors or Overfishing－
Kyuji WATANABE,1 Kazumi SAKURAMOTO,2 Hideki SUGIYAMA3 and Naoki SUZUKI21

National Research Institute of Far Seas Fisheries, Fisheries Research Agency,
Shizuoka-shi, Shizuoka 424-8633, Japane-mail: watanabk@fra.affrc.go.jp
2
Department of Ocean Science, Tokyo University of Marine Science and Technology,
Konan, Minato-ku, Tokyo 108-8477, Japane-mail: sakurak@s.kaiyodai.ac.jp
3
Akita Prefectural Fisheries Promotion Center, Oga-shi, Akita 010-0531, Japane-mail: sugipref@akita.lg.jp

Abstract
Sandfish (Arctoscopus japonicus) catch fluctuations both in Korea and Akita Prefecture, Japan,
coincided closely until the mid 1970s, although each of the catch derives from different stocks. After
that, however, the pattern of catch fluctuations in Akita was differed considerably from that in Korea,
i.e., the amount of the catch has been very low since the mid 1970s. However, no mechanism behind thesimilarity and differences in catches between Korea and Akita has been demonstrated so far. The aim of
this study is to investigate mechanisms behind these catch fluctuations using the information on ocean
environment and catch forecasting model developed by Sakuramoto et al. (2001). The result is that thestock depletion occurring in the mid 1970s was due to environmental factors and after that the heavy
decline in catches in Akita was due to overfishing. The important thing in managing a fish stock is to
avoid putting pressure on fish by high fishing intensity, which has already been depleted, and to avoid
losing a chance to recover abundance of fish depleted due to high fishing intensity.
Key words: Akita, catch forecasting, fisheries management, Korea, regime shift, sandfish,
water temperature

1. Introduction

offshoer fishinggroundcostal fishinggroundNorthern ‘Sea of Japan’ sandfish, Arctoscopus
japonicus, are one of the most important fish for thepeople of Akita Prefecture, Japan. Fishing for sandfish
has been done in two areas (Fig. 1). One is offshore
and the other, in coastal waters. The offshore fishinggrounds are formed along a stratum of 200-300 m
depth. A Danish seine fishery has been operating in
the offshore fishing grounds throughout the year,
except for the months in which fishing is closed. In
the coastal waters, set net and gillnet fishing gears
have been used for harvesting the spawning stock that
migrates to the coastal waters mainly in December.
The high season of the coastal fishing is, however,very short and lasts only a week in each coastal
fishing area (Sugiyama, 1989, 1990, 1991, 1992).
The sandfish catch in the coastal waters off Akita
Prefecture amounted to more than 10,000 tons from1963 to 1975. From 1976, however, it began to decrease sharply and fell to only 74 tons in 1984. There
Global Environmental Research9(2)/2005: 131-137
printed in Japan－300m

Hachimori

Akita Prefecture－ 200mCape Nyudo

Stn.1
Stn.2
Akita City

Oga Peninsula

Nikaho
50km

136 °

140 °

144 °E

44 ° N

Japan Sea
Akita Pref.
40 °

36 °

Pacific Ocean

Fig. 1 Locations of fishing grounds for sandfish
and sampling points for water temperature
off Akita Prefecture.
©2005 AIRIES

132

K. WATANABE et al.

has been much debate why the catch has decreased soheavily. Some claim that it was due to overfishing(Mizuguchi & Shibata, 1992), and others argue that itwas caused by environmental conditions (Sakuramoto
et al., 1997). Kawasaki (1983) implicitly noted theoccurrence of a regime shift by showing that patternsof fluctuations in sardine catches in Europe, Chili,
California and the Far East of Pacific were very similar to each other. Since then, the regime shift theory
has become popular. A regime shift is defined as ‘what
occurs when the climate has abruptly changed withina shorter period than that of the population fluctuation(Yasunaka & Hanawa, 2002).’ or ‘basic global systems that are constructed as a result of shifts in climate (atmosphere), oceans and ocean-ecosystems in a
decadal time scale’ (Kawasaki, 1983). Some people
believe that the ocean environment is the cause ofcatches fluctuations (Kawasaki, 1983; Noto & Yasuda,
1999; Oh et al., 2002; Nihira et al., 2003). However,there has been no explanation of why the sandfish
catch in Akita Prefecture was heavily depleted.
The aim of this study is to elucidate the mechanism behind the fluctuation in the sandfish catch. In
other words, we would like to clarify which is themain cause of the catch fluctuations, environmental
factors or overfishing.

2. Materials and Methods
2.1 Catch data and environmental information
used in this study
We used the following catch data, water temperatures and years of the regime shifts for the analysis.
1) The annual catches of sandfish by set net fishingand Danish seine fishing off Akita Prefecture from1961 to 1998 (Anon., 1998).
2) The mean water temperature in depth strata of
0-50 m, 75-150 m and 200-300 m at Station 1 from
April to December, from 1961 to 1998 (Anon., 1998).
Station 1 is located along this 200-300 m depth contours at 9 km off Cape Nyudo (Anon., 1998) (Fig. 1).
3) Statistics on offshore trawl fishing in area off
the Sea of Japan (Anon., 1978-1998).
4) The annual catches of sandfish by trawl fishing
off the east coast of the Korean Peninsula from 1961
to 1998 (Anon., 1965-1998).
5) The annual catches of sandfish by gill net
fishing and trawl fishing in the western Sea of Japan
from 1961 to 1998 (Anon., 1989).
6) The years when the regime shifts occurred(Yasunaka & Hanawa, 2002).
The word ‘Korean catch’ used in this study indicates the sum of the catches harvested from Koreanwaters by Korean fishermen and those harvested fromthe western Sea of Japan by Japanese fishermen, because the sandfish caught in these areas are the same
stock, called the ‘Eastern Korean Peninsula stock’(Okiyama, 1970; Fujino & Amita, 1984; Watanabe
et al., 2003). In Korea, sandfish are not valuable andare landed only as a by-catch by the walleye pollack
fisheries. Thus, from Korea there is little biologicalinformation such as migration patterns, the locations
and depths of their habitats, the age-composition oflanded fish, and so on. On the contrary, in Akita,
plenty of biological studies on sandfish have been
conducted. Therefore, our detailed investigation of therelationship between sandfish catches and environmental conditions will be conducted mainly using datacollected in Akita.
2.2 Forecasting models
Using forecasting models developed by Sakuramoto
et al. (2001), we forecasted the coastal and offshore
catches. The coastal and offshore catches in years t, ct,
and ot, are calculated as follows:y = Ax c + ε c(1)

z = Ax o + ε o(2)The vectors y and z are as follows:y = (ln c1 ln c2 • • • ln ck )T(3)

z = (ln o1 ln o2 • • •(4)ln ok )

T

Here, T and k denote the transpose of the vector
and the number of data, respectively. The terms εc andεo denote the vectors of error terms and each elementof εc and εo follows the normal distribution, with themean of zero and variances σc2 or σo2, respectively.
The variables xc and xo are also vectors withdimensions of two and four, respectively. The
elements of vectors xc and xo are as follows:x c = (α 0 α1 α 2 α 3 )T(5)

x o = ( β1 β 3 )T

(6)The elements of matrices A and B are the catch
and water temperature transformed by equations(9) – (11).

A=⎡ 1 ui ,1 ui , 2 ui ,3 ⎤⎢ 1 ui +1,1 ui +1, 2 ui +1,3 ⎥
⎥
⎢
•••
⎥
⎢
⎢⎣ 1 u k ,1 u k , 2 u k ,3 ⎥⎦

(7)

B=

u i ,3 ⎤⎡ ui ,1⎢ ui +1,1 ui +1,3 ⎥
⎥
⎢
•••
⎥
⎢
u k ,3 ⎥⎦⎢⎣ u k ,1(8)Here, k denotes the number of data. The elementsof the matrices ut , • are transformed as follows:
ut , 1 = ln(ct −1 )(9)ut , 2 = ln(ct − 2 )(10)ut , 3 = ln(w9, t −1 + w9, t − 2 + w9, t − 3 )(11)Collapse of the Arctoscopus japonicus Catch in the Sea of Japan

Here, w9,t denotes the water temperature atstation 1, at the depth of 200-300 m in September ofyear t. The parameter vectors xc and xo can be
estimated by the least square method. Using xc and xo
estimates, we can extrapolate the catch in thefollowing year as follows:cˆk +1 = exp( [ 1 u k +1,1 u k +1,2 u k +1,3 ] xˆ c )oˆ k +1 = exp( [ u k +1,1

u k +1,3 ] xˆ o )

(12)
(13)

Here, ^ denotes the estimated variable or matrices.
2.3 Simulation tests
As mentioned before, from 1976 to 1979, thecatches in Akita and Korea drastically decreased,
however, the catch in Korea increased again after
around 1980. On the contrary, in Akita, the catch has
continued at a very low level without recovery sincearound 1980. It is recognized, however, that the catchshowed an increase from 1979 to 1980 (see allow in
Fig. 2). Figure 3 shows that one to three years prior
to 1979, the water temperatures changed from cool towarm. This would indicate that the environmental
condition changed from a decreasing condition to an

Fig. 2 Trajectories of catches harvested in Akita andKorea. Circles indicate the years when regime
shifts occurred. The allow indicates a year
when the catch in Akita seemed to have an
increasing tendency.

133

increasing condition, as Korean catch indicated. Thus,
it is thought that the catch in Akita would haveincreased if the fishing had not continued sointensively. In order to demonstrate this, we conducted
the seven following simulations. Scenarios 1-4 arecases in which fisheries were closed for one year,
including both offshore and coastal fisheries. The yearof closure is 1978 in scenario 1, 1979 in scenario 2,
1980 in scenario 3 and 1981 in scenario 4. Scenarios
5-7 are the cases when 10%, 20% or 30% catch
reduction from 1978 to 1980 were conducted insteadof one-year fishing closure. In these simulations, we
assumed that the amount of catch by the coastal
fisheries was proportional to the spawning stock
biomass, because the coastal fisheries, which use, forexample, set nets or gill nets, are passive fisheries andonly fish migrating to the coast for spawning are
harvested. If the fish could escape being harvested by
the offshore fisheries, they would also migrate to thecoast for spawning that year or the following year.
Then, for simplicity, in this simulation we assumed
that both the catches that escaped harvesting due tothe closure were incorporated into the spawning stock
biomass (SSB).
For the simulation trials, we define the following
notations:
Nt ; number of fish at year t
R ; ratio of migrated fish to the coast for spawning
R·Nt ; number of migrated fish to the coast for
spawning(1− R) Nt; number of fish stay in the offshore waters
Eo ; exploitation rate in the offshore waters
Ec ; exploitation rate in the coastal waters
NSt ; number of spawning stock in the coastal area
in year t
efc ; effective factor due to catch regulation in the
coastal waters when a reduction rate of catchis d
efo : effective factor due to catch regulation in theoffshore waters when a reduction rate ofcatch is d
For simplicity, we assumed that R, Eo and Ec areconstant regardless of year. The catch in the coast andthe number of spawning stock are calculated by equations (14) and (15).
ct = Ec R N t(14)
NSt = (1 − Ec ) R N t(15)

From equations (14) and (15), we obtain,
NSt =Fig. 3 Trajectories of water temperatures in the depth
strata of 0-50 m, 75-150 m and 200-300 m at
Station 1 from April to December from 1961
to 1998 (Anon., 1998). The horizontal lines
indicate the mean water temperature in each
depth layer.

1 − Ecct
Ec(16)

We define the effective factor in the coastal waters
as follows:efc =d ⋅ ctd ⋅ Ec
=
NSt
1− Ec

(17)

Here, d=1.0 indicates the complete closure of fishing, and d=0.1, d=0.2, and d=0.3 corresponds to the134

K. WATANABE et al.

cases in scenarios 5, 6 and 7, respectively. That is, efc
is scaled with the amount of catches that protected byclosure or catch reduction comparing to the NSt when
the fishing is operating without fisheries closure or
any regulation. On the offshore waters, we defined theeffective factor as follows:
efo = Rd ⋅ otd ⋅ Eo= R(1− Eo ) (1− R) Nt
1 − Eo(18)

That is, the potential catch that is necessary toforecast the catch in the following year is calculated
by equation (19). After a one-year closure, it is assumed that the surplus catch that would be incorporated into the SSB decreases with the survival rate S,
which is including a fishing mortality. In this case, we
extrapolated the potential catches, using equations(12) and (13), which would have been harvested whenno regulation was enforced. In order to extrapolate thecatch in the following year, ct' is calculated by equation (19), i.e., during and after the year of closure, ct'
is used instead of ct in equations (9) and (10).
ct ' = ĉtt<K
ct ' = ĉt (1 + ef c ) + ôt ef o
t=K
(19)
t≥K
c t ' = ĉ t + c 'K S t − K
In the case of scenarios 5-7, i.e., the cases when
10%, 20% or 30% catch reduction from 1978 to 1980
were conducted instead of one-year fishing closure, ct',
is calculated by equation (20)ct ' = ĉtt < 1978ct ' = ĉt + d

t − 1978∑i =0{ ĉt (1 + ef c ) + ôt ef o } S i
t = 1978, 1979, 1980

ct ' = ĉt + [d1980 − 1978∑i=0

{ ĉ1980 − i (1 + ef c ) + ô1980 − i ef o }S i ] S t −1980

t > 1980(20)
For simplicity, in the simulations, we assumed thatR = 0.5, Eo = 0.3, and Ec= 0.5. Then the average exploitation rate for offshore and coastal waters is 0.4, and if
natural mortality coefficient per year is assumed to be
0.3, the average survival rate becomes S = exp(–0.9).

3. Results
3.1 Comparison of the catches between Akita andKorea
Table 1 shows some part of parameters estimatedby least square method. Figure 2 shows the respective
catch trajectories in Akita Prefecture and Korea. The
catch in Akita shown here denotes the total catches,
the summation of the catches harvested by coastal andoffshore fisheries. The pattern of catch trajectories in
Akita and Korea are very similar to each other before
the 1980s. That is, the catches increased from the
1960s, and became maximum around 1970. After thatthe catches decreased steeply. However, after the mid
1980s, the pattern of these two trajectories behaved
differently. That is, the catch in Korea increased again

Table 1 Parameters estimated and the years that the data areused for estimation.
Year
α0
α1
α2
α3
1964-1970–1.11210.3732
0.34731.2313
1964-1971
2.76630.31640.21040.5672
1964-1972
2.88840.31630.20670.5374
1964-1973
2.7046
0.31330.21850.5717
1964-1974
2.87260.30490.21430.5542
1964-1975
0.33920.27250.33891.0942
・
・
・
・
・
・
・
・
・
・
・
・
・
・
・
1964-1997
0.99530.7208–0.1929
1.1170after the beginning of the 1980s; however, that in
Akita remained low.
The black and white circles shown in Fig. 2 indicate years when regime shifts occurred (Yasunaka &Hanawa, 2002). The Korean catch fluctuations coincided well with these regime shifts. That is, the firstregime from 1958 to 1970 and the third regime from1977 to 1988 correspond to increasing phases of thecatch. The second regime from 1971 to 1976 and thefourth regime starting from 1989 correspond to decreasing phases of the catch. The catch fluctuations in
the first increasing and first decreasing phases also
coincided well with the catches in Akita, but differ
sharply from the Korean catch after the end of the
1970s. Why did this difference occur? We will discuss
this later.
3.2 The relationship between water temperatureand catch in Akita
Figure 3 shows the trajectory of water temperatures in depth strata 0-50 m, 75-150 m and 200-300 m
at Station 1. The three horizontal lines show the meanvalues in each respective depth layer. Figure 3 demonstrates that in the 1960s, many years showed watertemperatures higher than average, but, in the middleof the 1970s, the water temperatures suddenly decreased. After the 1980s, not so many cases of highwater temperatures were recognized and the temperature were rather low. These patterns of water temperatures and catches coincided well.
3.3 Fishing intensity
Figure 4 shows the ratio of the catch harvested by
the offshore fisheries to the total catch harvested by

Fig. 4 The ratio of catch harvested by the offshore fisheries
to the total catch harvested by the offshore and coastal
fisheries combined.

Collapse of the Arctoscopus japonicus Catch in the Sea of Japan

offshore and coastal fisheries. The ratio has steeply
increased since 1975, when the amount of the catch
drastically decreased. The target fish for the coastal
fisheries is only the spawning stock migrating to thecoast, but, the offshore fisheries harvest immature andmature fish before they migrate to the coast for
spawning. Thus the abrupt increase in the ratio meansthat overfishing had occurred in the offshore area andthis prevented the population from recovering fromlow stock levels.
3.4 Results of simulation tests
We show the results of scenarios 1- 4 in Fig. 5 andscenarios 5-7 in Fig. 6. Table 2 shows the tons ofcatch protected due to the fisheries closure or 10%,
20% or 30% catch reductions. For instance, in the caseof scenario 1, the forecasted catch in 1978 was 3,533
tons, and the one-year closure meant that everyone
forfeited this amount of catch. This means that a great
number of fish could escape harvesting and spawn
their eggs. Catch trajectories in both Akita and Korea
showed that the catches in 1980 were greater thanthose in 1979 (see Fig. 2). This indicates that theoceanographic conditions were conductive to popula-

135

tion rehabilitation. Thus, as is shown in the upper leftof Fig. 5 (scenario 1), the catch recovered rapidly by
5,000 tons. However, in the case of scenario 2, theforecasted catch in 1979 was small, only 1,389 tons.
This meant that oceanographic conditions were not sogood, and furthermore, the number of fish that could
escape harvesting was very a few. As a result, thecatch could not recover, as shown in the lower left ofFig. 5 (scenario 2). The same explanation holds forboth scenarios 3 and 4. The trajectory of the catch
derived from scenario 1 was similar to that observed
for the Korean catch.
Figure 6 shows the cases when catch reduction was
conducted instead of closure, because it is generally
very difficult to achieve complete fisheries closure.
When a 10% catch reduction was conducted from1978 to 1980, the effect of the reduction was not sohigh. However, when a 20% catch reduction was conducted from 1978 to 1980, the effect of the reduction
was high enough, and almost the same as that of the
one-year closure commencing in 1978. In this case,the total catch reduction was 1,800, much smaller thanthat for scenario 1. The effect of a 30% catch reduction was higher than that of the 20% catch reduction.

Fig. 5 Results of simulation tests when one-year fisheries closures were enforced.
Solid and broken lines indicate the observed and simulated catch trajectories, respectively.

Fig. 6 Results of simulation tests when three-year catch reductions were enforced.
Solid and broken lines indicate the observed and simulated catch trajectories, respectively.

136

K. WATANABE et al.
Table 2 The amount of catch forfeited due to fisheries closure or catch reduction.
Total catch reduction donotes the total catch forfeited during the three year peroid. Figures in scenarios
1- 4 and the first figures in the parentheses in scenarios 5-7 were forecasted catch using the forecastingmodel.
1978
scenario 1

1979

1980

1981

Total catch reduction

3,533

scenario 2

1,389

scenario 3

1,898

scenario 4

1,935

scenario 5353 (= 3533*0.1)

259 ( 2591*0.1)

260 ( 2597*0.1)

872

scenario 6
scenario 7

706 (= 3533*0.2)
1,060 (= 3533*0.3)

518 ( 2591*0.2)
777 ( 2591*0.3)

576 ( 2878*0.2)
950 ( 3165*0.3)

1,800
2,787

4. Discussion
In this study, we assumed that the exploitation ratein the coast is 0.5. However, the true rate would bemuch higher than this assumption. If Ec is grater than0.5, the efc becomes greater than 0.5 d/(1 − 0.5), i.e.
the effect of regulation would be higher than the casepresented in the simulations. Therefore, the result of
the simulation shown here would be an underevaluation of the catch regulations. Equally, if Eo isgrater than 0.3, the efo becomes grater than 0.3Rd/(1 – 0.3), i.e. the effect of regulation would be higher
than the case presented in the simulations. However,in the case of offshore fisheries, there is a possibility
that the Eo is smaller than 0.3. If Eo is smaller than 0.3,
the efo becomes smaller than 0.3Rd/(1 – 0.3), i.e. theeffect of regulation would be smaller than the casepresented in the simulations. However, the difference
would not be so large. If R is grater than 0.5, the effectof catch reduction will be grater than the case shownin the simulations, and vice versa.
The idea of regime shift has gained popularity andis a useful tool for explaining populations and catch
fluctuations. However, as was shown in this study, it isalso very important to evaluate the effect of harvesting.
The results of this study are summarized as follows:
1) The catch fluctuations in Korea occurred due toenvironmental factors. These coincided well with theregime shifts that occurred in 1957/58, 1970/71,
1976/77 and 1988/89, i.e., the first regime from 1958
to 1970 and the second regime from 1971 to 1976
corresponded to increasing phases, while the third
regime from 1977 to 1988 and the fourth regime starting from 1989 corresponded to decreasing phases.
2) The catch fluctuations in both Korea and Akita
coincided well before the middle of the 1970s, i.e.,
before the second regime ended in 1976. After that,
however, the pattern of catch fluctuations in Akita
differed from those in Korea. In Akita, the amount of
the catch has been very low since the middle of the
1970s.
3) The ratio of the catch harvested by the offshore
fisheries to the total catch harvested by the offshore
and coastal fisheries combined has increased steeply
since 1975, when the amount of catch drastically decreased. This means that high intensity of fishing had

injected in the offshore area and this prevented the
population from recovering from a low stock level.
4) The results of the simulation tests indicated that if
catch reduction had commenced during the beginningof the third regime, the catch would have increased
again and the trajectory of the catch in Akita would
have been similar to that in Korea.
5) The important thing about catch reduction is its
timing. If it is conducted in the year when the environmental conditions are not so good and stock abundance is very low, the effect of management is low.
Thus it beans repeating that catch reductions or fisheries closures should be commenced during years whenenvironmental conditions are good, before stock abundance has been heavily depleted.
The conclusion of this study is that the stock depletion occurring in the middle of the 1970s was dueto the environmental factors, and the heavily reduced
catch in Akita after that year was due to overfishing.
The important thing when we manage fish stocks is to
avoid putting pressure on the fish which are alreadydepleted due to high fishing intensity, and to avoid
losing a chance to rebuild their population level.

Acknowledgments
We wish to thank Dr. Matsuda, Yokohama National
University, for his constructive comments and help.
We also thank the members of the Akita Prefectural
Fisheries Promotion Center for their help.
References
Anonymous (1998) The report of the biology and resource
management of Sandfish. Akita Prefectural Fisheries Experimental Satiation, Akita, 1-11. (in Japanese)
Anonymous (1965-1998) The annual statistics of Agriculture,
Forestry and Fisheries in Korea. Ministry of Affairs andFisheries, Korea. (in Korean)
Anonymous (1978-1998) Statistics on offshore trawl fishery inarea off Japan Sea. Japan Sea National Fisheries ResearchInstitute, Fisheries Research Agency. (in Japanese)
Anonymous (1989) Fishing conditions of sandfish in Tottori
Prefecture. Report of Sandfish Ecology and Management,
Akita, Yamagata, Tottori and Shimane Prefectural Fisheries
Experimental Station, 53-81. (in Japanese)Collapse of the Arctoscopus japonicus Catch in the Sea of Japan
Fujino, K. and Y. Amita (1984) Subpopulation identification of
the sailfin sandfish from Waters Adjacent to Japan. Fish
Genetics and Breeding Science, 9: 31-39. (in Japanese).
Kawasaki, T. (1983) Why do some pelagic fishes have wide
fluctuations in their number? — Biological basis of fluctuation from the viewpoint of evolutionary ecology. In: Sharp,
G.D., Csirke, J., eds., Reports of the Expert Consultation to
Examine Changes in Abundance and Species Composition of
Neritic Fish Resources. FAO Fisheries Report, 291(3):1065-1080.
Mizuguchi, K. and R. Shibata (1992) Research method forsandfish (Arctoscopus japonicus) study. Report of Sandfish
Research Council, Japan Sea National Fisheries ResearchInstitute, 5, 30. (in Japanese).
Nihira, A., S. Suno and K. Takahashi (2003) Regime-shiftobserved in the demersal fishes in Sanriku and Jyoban (theeast-north of Honsyu, Japan) areas. Kaiyo Monthly, 35:
107-116. (in Japanese)
Noto, M. and I. Yasuda (1999) Population decline of the Japanese sardine, Sardinops melanosticus, in the relation to thesea surface temperature in the Kuroshio Extension. Canadian
Journal of Fisheries and Aquatic Sciences, 56: 973-983.
Oh, T., K. Sakuramoto and S. Hasegawa (2002) On the relationship between water temperature and catch fluctuations ofwalleye pollack Theragra chalcogramma in the northernwaters of the Japan Sea. Nippon Suisan Gakkaishi, 68:
866-873. (in Japanese with English abstract)
Okiyama, M. (1970) Studies on the population biology of thesandfish, Arctoscopus japonicus (STEINDACHNER) II,
population analysis (preliminary report). Bulletin of Japan
Sea Regional Fisheries Research Laboratory, 22, 59-69. (inJapanese)

137

Sakuramoto, K., T. Kitahara and H. Sugiyama (1997) Relationship between water temperature and fluctuations in sandfish
catch (Arctoscopus japonicus) in the coastal waters off Akita
Prefecture. ICES Journal of Marine Science, 54:1-12.
Sakuramoto, K., H. Sugiyama and N. Suzuki (2001) Models forforecasting sandfish catch in the coastal waters off Akita
Prefecture and the evaluation of the effect of a 3-year fisheryclosure. Fisheries Science, 67(2), 203-213.
Sugiyama, H. (1989) Some features recognized in sandfish
migrated to the coast of Akita prefecture. Report of Sandfish
Research Council, 3:33-41. (in Japanese)
Sugiyama, H. (1990) Tendency of sandfish catches in thewaters of northern Sea of Japan. Bulletin of the JapaneseSociety of Fisheries Oceanography, 54: 475-461. (in Japanese)
Sugiyama, H. (1991) Construction of fishing ground for sandfish in the waters northern Sea of Japan. Report of Experimental Research in the Sea of Japan, 21: 67-76. (in Japanese)
Sugiyama, H. (1992) On the ecology in spawning, time ofhatching and the number of eggs spawned of sandfish off the
Oga peninsula. Report of Northern Japan Bottom Fishdivision, 25: 11-25. (in Japanese)
Watanabe, K., H. Sugiyama, S. Sugishita, N. Suzuki and K.
Sakuramoto (2003) Estimation of distribution boundary
between two sandfish Arctoscopus japonicus stocks in the
Sea of Japan off Honsyu, Japan using density indices.
Bulletin of the Japanese Society of Fisheries Oceanography,
68: 27-35.
Yasunaka, S. and K. Hanawa (2002) Regime shifts found in the
Northern Hemisphere SST field. Journal of MeteorologicalSociety Japan, 80:119-135.

(Received 12 May 2005, Accepted 1 July 2005)